[fix]mapbox端经纬网去掉proj4 review by songym

Author: luoxiao-supermap

src/mapboxgl/overlay/GraticuleLayer.js

@@ -222,7 +222,7 @@ export class GraticuleLayer {
 
  _getDefaultExtent(extent, map = this.map) {
  const crs = (map.getCRS && map.getCRS()) || {};
- let { epsgCode, extent: crsExtent } = crs;
+ let { extent: crsExtent } = crs;
  if (!crsExtent) {
  crsExtent = [-180, -85.05119, 180, 85.05119];
  }